Fate of Human Fertilized Eggs during Prenatal Life: Present Status of Knowledge

Abstract

It was pointed out that the fate of human fertilized eggs is diverse. On the basis of the reported statistics together with some other informations, it is concluded that a fairly large portion of all zygotes formed among the total population is lost naturally during prenatal life. Next, it was demonstrated by our epidemiological survey on embryos of 3 to 10 weeks of fertilization age arising from mostly healthy mothers that the incidence of various malformations in such early prenatal stage is far higher than that in infants. The similar finding was also shown with respect to the prevalence of cytogenetic defects on the specimens from the same sources. Furthermore, our studies indicate that normal embryos show con- siderable variation in the relation between two of the three variables; developmental stage, CR length and menstrual age. The known and possible factors which determine the unfavorable fate of human offspring were discussed. In view of the present meagre knowledge in this respect, some suggestions were made on directions of future studies for clues to ensure the favorable prenatal human development. © 1970, Editorial Board of Okajimas Folia Anatomica Japonica. All rights reserved.